Self-filtering composition.



UUATING 0R PLASTIC. "dfb, 99 1 C. L. NORTON. FILTBRING COMP() 0N.

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UNITED STATES www.

PATENT OFFICE.

SELF-FILTERIN G COMPOSITION.

Specification of Letters Patent.

Application led July 6, 1908.

Patented July 27, 1909.

Serial No. 442,042.

To all whom 'it may concern:

Be it known that I, CHARLES LADD NOR- TON, a citizen of the United States, and resident of Manchester, in the county of Essex and State of Massachusetts, have invented new and useful Improvements in Self-Filtering Compositions, of which the following isa specification.

My invention consists of a self-filtering composition and relates to the production of compacted material from which mixtures containing fibrous material and solid or semi-solid cementitious matter and, initially at least, a liquid such as is usually required to insure the proper performance of the functions of the cementitious material.

Particularly, my invention relates to the production of refractory materials from substances of which asbestos is a type, for instance such refractory materials as are de scribed in Letters Patent of the lUnited States No. 847,293, granted to me under date of March 12, 1907.

Moreover, my invention herein described relates to the roduction of such refractory materials by t e compression of the mixed ingredients of which they are composed, and the object of this invention is to facilitate and expedite the manufacture of such substances and to contribute to their industrial productionthe benefits of certainty of process and uniformity of product.

Where as in the case of the refractory material described in my patent aforesaid, the ingredients which are subjected to pressure (namely, the fibers of the cementitious material and the liquid) are placed in a filter press, thefiltration of the surplus liquid from the mixture must be effectuated in such manner that the liquid expressed may not carry with it too much of the cementitious material, which to perform its function properly, must remain in the body of the material together with a sufficient residual quantity of water to effect the setting of the cement. Consequently, if ltering material on a filter bed is relied upon to retain the finely comminuted material, the mesh thereof must be extremely fine, in most cases as fine as bolting cloth, if its functions are to be properly performed.

While the employment of fine textile filtering material 1s mechanically feasible and effective to produce slabs or sheets of refractory material of the general character above indicated, yet such ltering webs are undesirable and troublesome in a continuous series of operations, principally for the reason that they very soon become impregnated with cementitious material which sets in the mesh and renders the filter thereafter useless and also because such filter webs are fragile and ill suited to sustain heavy pressure; even though carefully supported. It is for this reason, I believe, that the manufacturers of certain refractory materials containing hydraulic cement have resorted to the formation of sheets by flowing a stream composed of fibers (such as asbestos) h draulic cement and an abundance of WatFLupm forming screens of paper machines, and have subse uently superposed sheets thus formed, after t e manner of card board manufacture, rather than adopt treatment'by combined pressure and filtration, although a lterpressed body containing the ingredients above named is superior in many respects to the laminated structures heretofore made.

My invention in its broader aspect, is characterized by the formation of a mixture of the essential ingredients, namclyz-fibers, solid or semi-solid; cementitious material, and a suitable liquid,-of such character and consistency that, when a mass of such mixture is spread upon a perforated metal screen, the fibers of the mlxture will, by interlacing and feltin automatically and of themselves, form fiilration Webs over and across relatively large perforations in a filter sheet, so that these foundation fibers themselves furnish a filter web of fineness sufficient to retain within the body of the material the cementitious material, while allowing surplus liluid to be expressed. In properly compoun ed mixtures constituted princlpally of asbestos fibers (even those very short fibers produced 5y the grinding of serentine rock) these foundation fibers of the mlxure form an effective retaining ltration web over apertures in a perforated metal sheet 1/16 1n diameter. The physical condition essential to the performance of this function by the fibers in the mass under treatment is that the proportion of liquid in the material shall be less than that which would produce mobility ofthe fibers in the liquid. If too much liquid is employed so that the fibrous ingredients of the material float about it, as soon as the mixture is placed upon a filter bed provided only with a erforated metal sheet, the fibers themse ves and a large portion of the cementitious maia I terial escape through the perforations, thus de riving the mixture of part of a very essentia ingredient, for the reason that the cementitious material is usually very finely 5 comminuted. Again, if the cementitious material with or without a portion of the fiber escapes through the mesh or perforations in the filter bed, the s aces in the filter bed soon become clogge and, as the cementitious material sets, the functional utility of the filter bed is destroyed, and if it be used in a hydraulic press the filtration sheets and webs become firmly cemented to the head of the press, from which they can be removed only with great difficulty. It is hardly necessary to state that, while the proortion of the liquid in the material should e less than that which will produce mobility of the fibers therein, it should be at least sufficient for the purpose of combination with the cementitious material. This condition, however, is very easily secured without danger of exceeding the proper maximum limit.

In the drawings hereto annexed there is illustrated conventionally in part and on a very much enlar ed scale, a ortion of a filter press and its be showing t e characteristic ehavior of a self filtering composition which embodies my invention.

This invention comprises the self-filtering com osition and also the process which the emp oyment of such composition involves. The process which is described herein in order to illustrate fully the value and mode of operation of the self-filtering composition is described in an application for patent filed concurrently herewith serially numbered 442,044 and is reserved for claim therein; in

its specific asplect also one of the filtering compositions erein described is also described in another application for patent Serial Number 442,043 filed by me concurrently herewith and is reserved for claim therein.

As stated hereinabove, the compositions, for the production of refractory material of the class to which my invention relates consists of fibrous cementitious material and the liquid required for the functional o eration of the cementitious material in an among the fibers. One takes, for instance, a mass of fibers of which asbestos is a type, these may either be asbestos bers as ordinarily understood or may consist of the fibrous pulp roduced by rinding the serpentine roc fiom which as estos 1s mined. With these fibers, preferably in a dry state, there is mixed a suitable quantity of dry hydraulic cement; suitable proportions are ten to twelve parts by weight of h draulic cement Portland cement) and twenty parts 5y weig o as es os fiber. When these are thoroughly mixed, to the dry mixture there is added a quantity of water sucient to .effect the proper setting of the cement, (allowance being made for the water which 1s subsequently to be pressed out of the material) but less than that quantity of water which, when thoroughly mixed with the fiber and cement, will render the fibers mobile in the liquid. Assuming that the solid ingredients mixed in the proportions above stated are dry, a proper proportion will be fifty parts of water by weight. Then this uantity of w-atr-ls' mixed thoroughly with t e solid ingredients, the entire mass is of the consistency of a wet mush of which the solid portion will retain the water temporarily at least without allowing any sensible portion thereof to drain off or settle. This mixture is then placed upon the filter bed of the filter ress. p Referring to the drawings; A and B represent the upper and lower press heads or press lates. Upon the lower press plate there is aid a sheet of woven wire E and over this a sheet of perforated metal C. The perforations in this sheet S should be close together and preferably quite small, though they may, without impairing the success of the rocess, be as large as 1/16 in diameter bmaller perforations, even as small as 1/64 are, however, preferable for the reason that by the use of smaller erforations the lower 9- surface of the finished) compressed product is more nearly plane than it is when larger perforations are employed. Practice and experience with the particular mixture of materials used as ingredients of the article of manufacture produced, will determine more exact-ly the proper diameter and s acing of the a ertures in the to of the ter bed. The o ject to be attaine is the formation of webs or nets composed of the fibers which form an ingredient of the material, over and across the erforations in the filter bed sheet, and t e preservation of these webs during the compression stage of the rocess so that, while surplus liquid will pass t rough the self-formed webs of fiber, the cementitious material will be retained within the body of the article produced.

Referring again to the drawing, F represents the fibers in the mass under pressure, and the dots (not lettered) represent the particles of cementitious material. When the mixture as above described is spread upon the filter bed and subjected to pressure between the plates A and B, simultaneously with the initial flow of li uid through the apertures in the perforate sheet C the foundation fibers mat together and form a web as at F stretched across the apertures in the sheet C. The web possesses sufficient tensile strength to retain its integrity even though the pressure between the press plates A and B exceed one ton to the s uare inch. These webs of the foundation fi ers retain the cementitious material, while allowing COATING R PLASTIC.

surplus water to esca e. When, after the compressed sheet or s ab is removed from the press, it is examined closely, the lower surface of it will be found covered with slight protuberances, showing where the retainin webs of the foundation fibers have sagge sli htly into the apertures of the top sheet of t e filter bed, and it has also been observed in many instances that the cementitious material is more dense immediately behind these little protuberances than elsewhere in the body of the finished article. This apparently demonstrates the tendency of the finely comminuted cementitious material to flow toward and to escape from the body of the mixture under pressure and also demonstrates the effectiveness of the selfformed webs of foundation fiber to prevent the escape of the cementitious materlal from the body of the mixture.

If the mixture under treatment is of the character described in my patent aforesaid, the following s ecifications are recommended. The ingre ients being asbestiform fiber,

finely divided magnesium oxid, and water, one proceeds by first mixing in a dry state rom to 3 prts by wleight of) the asbestiorm er wit 1 art y weig t of ma nesium oxid the latlier being preferab'li'r cure y he calcination of finely divided magnesium carbonate as set forth in my said patent. Then 1 part by weight of this mixture of asbestiform fiber and ma nesium oxid 1s mixed wif-li 2 parts 5y weiglt of water.

These proportions are correct provided the solids are thoroughly dry; if they have laid for any length of time in a moist atmosphere, water absorbed from the air must be taken account of. The correct manipulation and 40 adjustment of the proportion of water mechanically added must be learned by ex erience and checked b observation. '.[Phe quality of the wet mus and also the behavior of the mixture in the press will serve as checks u on the operation of water addition. Too littli; water will cause the compressed sheets or plates to adhere too intimately to the press head and too much water will manifest its excess by the quality of the liquid which flows from the press. The expressed li uid should run from the press nearly clear; if 1t is milky, then it is certain that too much water is being added to the material in the preparation for the ress. A slight milkiness or cloudiness o the water which first emerges from the press will always be observed but it is of no consequence. It is the subse uent flow of which the character serves as a etector of an excess of water in the mixture. Conversely the character of the waste water from the press for the same reason will betray error in mixing the dry solid ingredients; if these involved too scant proportions of fiber, the mobility of the fibers in the liquid added will allow fiber and cement to pour throu h the filter perforations, and the expressed iquid will flow cloudy throughout the operation.

The mlxed mass placed in the press is subjected to a pressure, preferably of one ton or more to the square inch. The foundation fibers, as illustrated in the drawing, form retaining webs over the perforations in the upper sheet of the filter bed and retain the magnesium oxid in the body of the article produced and insure the cementation of substantially the entire quantity of magnesium oxid originally incorporated in the mixture.

What I claim and desire to secure by Letters Patent hereby is as follows:

1. A self-filtering composition consistin of fibers, comminuted cementing materia and a liquid appropriate thereto, the proportion of theliquid being less than that productive of mobilit of the bers therein;

2. A selftering composition consistin of asbestiform bers, cementin material an a li uid appropriate thereto, t e proportion of t e liquid being less than that productive of mobility of the fibers therein.

3. A self-filtering composition consistin of asbestiform fibers, hydraulic cement an water, the proportion of water being less than that productlve of mobility of the fibers therein.

4. A self-filtering composition consisting of twenty parts by weight of asbestiform fibers, ten to twelve parts of hydraulic cement and fifty parts of water.

Signed by me at Boston, Massachusetts, 100 this fteenth day of June 1908.

CHARLES LADD NORTON.

Witnesses:

CHARLES D. WOODBERRY, JOSEPHINE H. RYAN.

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